Method and apparatus for transmitting downhole information from a well

Abstract

The specification discloses a method and apparatus for transmitting information to the surface from a downhole location in a well. A signal generating means is positioned at the downhole location and is operated to generate an acoustical pressure wave signal of constant frequency and phase state in a liquid medium, e.g., drilling fluid present in the well. Operation of the signal generating means is temporarily altered in response to the information to be transmitted to shift the phase state of the wave signal to a second phase state to thereby encode the information into the wave signal. Operation of the signal generating means is altered in such a way so that the shift in phase state is carried out in one normal sonic period of the wave signal. This provides, when the wave signal is synchronously rectified, an effective time for the phase shift equal to zero.

What is claimed is: 
     
       1. A method of transmitting information from a downhole location in a well through a liquid medium in the well, said method comprising: generating an acoustical pressure wave signal in said liquid at a point downhole in said well, said wave signal having a constant frequency and phase state; and   altering said wave signal in response to said information to be transmitted to shift the phase state of said signal, said shift of said phase state being carried out in a time period which produces, when said wave signal is synchronously rectified, a time for said phase state shift effectively equal to zero.   
     
     
       2. The method of claim 1 wherein said time period is equal to one normal sonic period of said wave signal. 
     
     
       3. The method of transmitting information from a downhole location in a well having a liquid medium in the well, said method comprising: generating an acoustical pressure wave signal in said liquid at a point downhole in said well, said wave signal having a constant frequency and phase state;   converting said information to be transmitted into a digital word having a plurality of bits; and   altering said wave signal in response to designated bits of said digital word to shift said phase state of said signal, said shift of said phase state being carried out in a time period which provides, when said wave signal is synchronously rectified, a time of shift of phase state which is effectively equal to zero.   
     
     
       4. The method of claim 3 wherein said time period is one normal sonic period of said acoustical pressure wave signal. 
     
     
       5. The method of claim 4 wherein said shift of said phase state of said wave signal equals -180°. 
     
     
       6. A logging-while-drilling apparatus comprising: a housing adapted to be positioned in a drill string of an earth drilling apparatus wherein a drilling fluid when circulated through the drill string will flow around said housing;   signal generating means positioned on said housing do that at least a portion of the drilling fluid flowing through the drill string will flow through said signal generating means;   at least one transducer means for sensing a downhole condition and producing a signal representative of said sensed condition;   a motor in said housing adapted to run at a constant speed; and   drive means for connecting said motor to said signal generating means so that said motor will drive said signal generating means at a set speed to thereby generate an acoustical pressure wave signal in the drilling fluid, said drive means including: shift means responsive to said sensed condition signal for temporarily altering said set speed of said signal generating means.     
     
     
       7. The logging-while-drilling apparatus of claim 6 wherein said signal generating means comprises: a rotary valve having a stator and a rotor, said rotor having a shaft connected to said motor by said drive means.   
     
     
       8. A logging-while-drilling apparatus comprising: a housing adapted to be positioned in a drill string of an earth drilling apparatus wherein a drilling fluid when circulated through the drill string will flow around said housing;   a rotary valve means positioned on said housing so that at least a portion of the drilling fluid flowing through the drill string will flow through said valve, said valve having a rotor with a shaft journaled in said housing;   at least one transducer means for sensing a downhole condition and producing a signal representative of said sensed condition;   a motor in said housing having a drive shaft; and   drive means for connecting said drive shaft to said shaft of said rotor so that said motor will drive said rotor at a set speed, said drive means including: shift means responsive to said signal representative of said sensed condition to temporarily change the relative speed between said drive shaft and said shaft of said rotor.     
     
     
       9. The logging-while-drilling apparatus of claim 8 wherein said drive means includes: a transmission having a case and an input connected to said drive shaft and an output connected to said shaft of said rotor, said transmission including: a set of planetary gears;   a ring gear cooperating with said set of planetary gears;   releasable means normally securing said ring gear to said case to prevent relative rotational movement between said ring gear and said case; and     wherein said shift means includes: means responsive to said signal representative of said sensed condition for releasing said releasable means to allow relative movement between said ring gear and said case.     
     
     
       10. The logging-while-drilling apparatus of claim 9 wherein said energy storage means comprises: spring means adapted to store a predetermined amount of energy for propelling said ring gear in a defined direction when said releasable means are released.   
     
     
       11. The logging-while-drilling apparatus of claim 10 wherein said energy storage means further includes: an inertia element of relatively large mass connected between said ring gear and said spring means.   
     
     
       12. The logging-while-drilling apparatus of claim 11 including: a winder means operable when the energy in said spring means drops below said predetermined amount to rewind said spring means to said predetermined amount.   
     
     
       13. The logging-while-drilling apparatus of claim 9 wherein said releasable means comprises: a clutch comprising: a first element attached to said ring gear;   a second element affixed against rotational movement with respect to said case but mounted for longitudinal movement therewith;   a spring normally biasing said first and second elements together to engage said clutch; and     means responsive to said signal representative of said sensed condition for moving said second element against the bias of said spring to disengage said clutch.   
     
     
       14. The apparatus of claim 13 wherein said means for moving said second element against the bias of said spring comprises: a solenoid.   
     
     
       15. Apparatus adapted for transmitting data signals from a well bore to the surface and comprising: a body adapted for connection in a pipe string and having a fluid passage arranged to carry fluids between the surface and well bore;   a first signal-producing member cooperatively arranged in said fluid passage for directing at least a portion of a fluid flowing therethrough along at least one selected flow path;   a second signal-producing member cooperatively arranged in said fluid passage adjacent to said first member for rotation to repetitively obstruct said flow path at periodic intervals for generating cyclic acoustic signals in a fluid flowing through said fluid passage; and data transmitting means including rotatable driving means, and signal-responsive coupling means intercoupling said driving means to said second signal-producing member, said coupling means being selectively operable in response to electrical data signals applied thereto for controlling the rotation of said second signal-producing member to produce at least one detectable change in the character of said acoustic signals representative of such electrical data signals.   
     
     
       16. Apparatus adapted for transmitting data to the surface during the drilling for a borehole and comprising: a body adapted for connection in a tubular drill string and having a fluid passage arranged to conduct drilling fluids between the surface and borehole-drilling device dependently coupled therebelow;   a flow director cooperatively arranged for movement in said fluid passage and including at least one opening for directing drilling fluids flowing through said fluid passage along a selected axis;   a signal-producing member coaxially arranged for rotation in said fluid passage and including a plurality of alternately-disposed openings and obstructions angularly spaced from one another and respectively adapted to successively cut across said axis upon rotation of said signal-producing member for producing cyclic acoustic signals in a drilling fluid flowing through said fluid passage;   motor means adapted for rotating said signal-producing member; and   data-transmitting means including signal-responsive coupling means co-rotatively intercoupling said motor means to said signal-producing member, said coupling means being operative in response to electrical data signals applied thereto for selectively shifting said signal-producing member between selected angular orientations during the continued rotation thereof to produce detectable changes in the phase relationships of said acoustic signals representative of such electrical data signals.   
     
     
       17. The apparatus of claim 15 wherein said detectable change is a change in the phase relationship of said acoustic signals. 
     
     
       18. The apparatus of claim 15 wherein said driving means include a motor adapted to be operated at a constant speed. 
     
     
       19. The apparatus of claim 15 further including: data signaling means on said body and adapted for producing said electrical data signals as an indication of at least one downhole condition.   
     
     
       20. The apparatus of claim 15 wherein said coupling means include: first and second coupling members respectively coupled to said second signal producing member and said driving means;   means intercoupling said coupling members together for orienting said second signal producing member in at least two different angular positions in relation to said first signal producing member; and   actuator means responsive to said electrical data signals for selectively moving said second signal producing member between its said different angular positions to produce said detectable change in the form of a change in the phase relationship of said acoustic signals.   
     
     
       21. The apparatus of claim 20 wherein said driving means include a motor adapted to be operated at a constant speed. 
     
     
       22. The apparatus of claim 20 further including: data signaling means on said body and adapted for producing said electrical data signals as an indication of at least one downhole condition. 
     
     
       23. The apparatus of claim 20 further including: means cooperatively arranged on said body for supplying electrical data signals which are a function of at least one downhole condition to said coupling means. 
     
     
       24. Apparatus adapted for measuring at least one downhole condition while drilling a borehole and comprising: a body tandemly coupled in a tubular drill string having a borehole drilling device dependently coupled thereto and defining a fluid passage for circulating drilling fluids between the surface and said borehole drilling device;   data signaling means on said body and adapted for producing digital data signals representative of at least one downhole condition;   acoustic signaling means on said body and including a flow directing member disposed in said fluid passage and having a plurality of spaced openings cooperatively arranged for directing drilling fluids in selected fluid paths along said fluid passage, a rotatable flow obstructing member in said fluid passage and having a plurality of alternately distributed angularly spaced openings and obstructions cooperatively arranged to successively cross said fluid paths upon rotation of said flow obstructing member for producing cyclic acoustic signals in drilling fluids flowing through said fluid passage, and motor means adapted for rotating said signal producing member; and   signal responsive coupling means co-rotatively intercoupling said motor means to said signal producing member, said coupling means being operable in response to said digital signals applied thereto for selectively shifting said signal producing member between selected angular orientations during the continued rotation thereof to vary the phase of said acoustic signals in accordance with said digital signals.   
     
     
       25. The apparatus of claim 24 further including: means adapted for connection to the surface end of said drill string for detecting at least changes in the phase of said acoustic signals to provide indications at the surface representative of said downhole condition. 
     
     
       26. The logging-while-drilling apparatus of claim 6 wherein said set speed of said signal generating means is altered for a time period equal to one normal sonic period of said acoustical pressure wave signal. 
     
     
       27. The logging-while-drilling apparatus of claim 8 wherein said shift means includes: energy storage means for providing energy to assist in effecting said change in said relative speed.